Historical clue formulations

• What acids do when mixed with bases — 2026-09-13
• Display some emotion, perhaps — 2026-08-16
• Flinch, say — 2026-04-27
• Gape or gasp, say — 2025-03-06
• Change, chemically — 2025-02-25
• Duck, say — 2024-11-15
• Respond to a stimulus — 2024-10-28
• Blink or jump, say — 2024-06-04
• Flinch, say — 2024-01-24
• Twitch, for instance — 2022-09-25
• Respond to a stimulus — 2021-09-22
• Flip, say — 2021-01-23
• DO something — 2020-03-30
• Blink or flinch, say — 2020-03-16
• Not just sit there — 2019-12-06
• What a person with a poker face doesn't do — 2019-08-30
• Flinch or twitch, say — 2019-07-14
• Undergo a chemical change — 2019-04-24
• Flinch, e.g. — 2018-12-29
• Respond to a stimulus — 2018-09-04
• Not be inert, as two chemical compounds — 2017-01-03
• Flinch, say — 2016-01-24
• Change color, maybe — 2015-03-28
• Not take it lying down — 2013-06-27
• Undergo a chemical transformation — 2013-05-28
• Ooh and aah, e.g. — 2013-01-12
• Turn another color, say — 2012-09-08
• Do a double-take, e.g. — 2010-12-21
• Not be deadpan — 2010-06-10
• Flinch, say — 2010-03-21
• Not keep a poker face — 2008-11-01
• Not just sit there — 2008-06-01
• Flinch, say — 2008-01-08
• Flinch or blink, say — 2007-05-28
• Do a double-take — 2007-04-11
• Change, chemically — 2007-01-25
• Strike back, say — 2006-07-26
• Change, chemically — 2006-04-16
• Don't just stand there — 2004-09-09
• Strike back, e.g. — 2003-11-14
• Strike back, say — 2003-05-06
• Flinch, say — 2003-01-29
• Jump at a noise, e.g. — 2002-10-06
• Make a move — 2002-05-26
• Respond to a stimulus — 2001-11-19
• Strike back — 2001-09-09
• Don't just stand there — 2001-06-25
• Flinch, say — 2000-11-23
• Strike back — 2000-04-25
• Push back, perhaps — 1999-08-29